Fudgy, glossy brownies made with high‑quality dark chocolate, butter, and a hint of espresso for an extra depth of flavor.
Warm up the oven to 175 °C (350 °F) and line an 8‑inch square pan with parchment paper, leaving overhangs for easy lifting later.
Gently melt all of the chocolate together with the butter in a heatproof bowl over simmering water, or in short microwave bursts. Stir until silky, then let it cool just a touch.
In another bowl, whisk together the eggs, granulated sugar and brown sugar until the mixture looks slightly thick and pale – this builds that shiny, crackly top.
Pour the melted chocolate‑butter blend into the egg‑sugar mixture while whisking gently. Add the vanilla extract and stir until the batter is glossy and uniform.
Sift together the flour, cocoa powder, salt and, if you like, the espresso powder. Gently fold the dry blend into the wet batter with a spatula, stopping as soon as no dry streaks remain. Toss in the chocolate chunks if you’re using them.
Spread the batter evenly in the prepared pan, smooth the top and bake for about 20–25 minutes. The edges should be set while the center stays a little soft – a toothpick will show a few moist crumbs.
Let the brownies cool in the pan for 15 minutes, then lift them out using the parchment overhangs and cool completely on a rack before slicing. For the fudgiest bite, chill them an hour before cutting.